Eisenhauer, Anton

Gutjahr, Marcus

Henkel, Daniela

Hiebenthal, Claas

Hu, Marian Y.

Jurikova, Hana

Krause, Stefan

Laudien, Jürgen

Liebetrau, Volker

Rollion-Bard, Claire

Schmidt, Mark

OceanRep

Geophysical Research AbstractsVol. 20, EGU2018-8970, 2018EGU General Assembly 2018© Author(s) 2018. CC Attribution 4.0 license.Incorporation of boron isotopes into brachiopod shell calcite: implicationsfor paleo-pH reconstructionsHana Jurikova (1), Volker Liebetrau (1), Marcus Gutjahr (1), Claire Rollion-Bard (2), Marian Y. Hu (3), DanielaHenkel (1), Claas Hiebenthal (1), Stefan Krause (1), Mark Schmidt (1), Jürgen Laudien (4), and AntonEisenhauer (1)(1) GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Germany (hjurikova@geomar.de), (2) Institut de Physique duGlobe de Paris, France, (3) Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Germany, (4)Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung Bremerhaven, GermanyThe boron isotope (δ11B) composition of marine calcifiers is considered to be one of the most reliable pH proxies,enabling us to reconstruct past ocean pH and infer on the associated changes in carbon budget involved (e.g. Gut-jahr et al. 2017). The application of the commonly used δ11B archives such as foraminifera or corals is howevermostly limited to the Cenozoic due to insufficient preservation or incomplete geological records. Brachiopods havea promising potential for extending our knowledge on seawater pH evolution throughout the entire Phanerozoicconsidering their high abundance in the fossil record and its origin dating back to the early Cambrian. Moreover,their shell is composed of low-magnesium calcite, rendering brachiopods more resistant to post-depositional di-agenetic alteration of its primary chemical signal (e.g. Brand et al. 2012). Additionally, even today they presentan extant and widespread taxa, allowing for an assessment of the controls on boron isotope incorporation intobrachiopod calcite and possible distortions of the signal due to vital effects or other processes.We present a detailed exploration of boron isotope systematics in three different brachiopod species (Magellaniavenosa, Terebratella dorsata, Pajaudina atlantica) cultured under controlled laboratory settings for over a year.Our experimental setup includes a control (pH = 8.15) and two pH treatments (pH = 7.6 and 7.35), and we provideboth bulk MC-ICP-MS as well as high spatial resolution SIMS data of the shell material. Our results indicate thatboron incorporation is primarily driven by vital effects related to their ability to regulate calcifying fluid pH inresponse to ambient changes, which we further validate by in vivo microelectrode measurements (e.g. Stumpp etal. 2012). Despite internal buffering, the local pH at calcification sites systematically decreases with seawater pH,and hence is impacted by ocean acidification. This not only suggests that brachiopod shells serve as useful andconservative recorders of past ocean pH trends, but also provides new insights into mechanisms that may haveenabled brachiopod survival throughout several major environmental crises in the past.Our findings have implications for past climate studies, as well as research on calcification processes and physio-logical adaptations to environmental change (e.g. the actual global ocean acidification).Brand, U., Posenato, R., Came, R., Affek, H., Angiolini, L., Azmy, K. and Farabegoli, E., 2012. The end-Permianmass extinction: A rapid volcanic CO2 and CH4-climatic catastrophe, Chem. Geol. 323, 121-144.Gutjahr M., Ridgewell A., Sexton P.F., Anagnostou E., Pearson P.N., Pälike H., Norris R.D., Thomas E., and FosterG.L., 2017. Very large release of mostly volcanic carbon during the Palaeocene-Eocene Thermal Maximum, Nature548, 573-577.Stumpp M., Hu M.Y., Melzner F., Gutowska M., Dorey N., Himmerkus N., Holtmann W.C., Dupont S.T.,Thorndyke M.C., and Bleich M. Acidified seawater impacts sea urchin larvae pH regulatory systems relevantfor calcification, PNAS 44: 18192-18197.

Incorporation of boron isotopes into brachiopod shell calcite: implications for paleo-pH reconstructions

http://oceanrep.geomar.de/43546/1/EGU2018-8970.pdf

Incorporation of boron isotopes into brachiopod shell calcite: implications for paleo-pH reconstructions

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